Method of and apparatus for annealing strip metal



Dec. 17, 1963 WILSON ETAL METHOD OF AND APPARATUS FOR ANNEALING STRIP METAL Filed Feb. 15, 1957 5 Sheets-Sheet 1 4 mm ml a, m\ mm A N Wm Q 1 1 AN N Am, n v9 INVENTORS. ZEE W/z :a/v fan 0v A. (OE V BY 7 ATTORNEY-51 Dec. 17, 1963 1.. WILSON ETAL 3,114,539

METHOD OF AND AF ARATUS FOR ANNEALING STRIP METAL 5 Sheets-Sheet 2 Filed Feb. 15, 1957 INVENTORS. 4 5 M4 50M A. (GE/v3 ATTORNEYS:

Dec. 17, 1963 L. WILSON ETAL 3,114,539

METHOD OF AND APPARATUS FOR ANNEALING STRIP METAL Filed Feb. 1:5, 1957 5 Sheets-Sheet 4 BY M Mar-M Dec. 17, 1963 w so ETAL 3,114,539

METHOD OF AND APPARATUS FOR ANNEALING STRIP METAL Filed Feb. 13, 1957 5 Sheets-Sheet 5 IN V EN TOR).

United States Patent Ofiice 3,114,539 Patented Dec. 17, 1963 3,114,539 NIETHOD OF AND APPARATUS FOR ANNEALING STRIP FETAL Lee Wilson, Lee Wilson Engr. Co. Inc, 20005 W. Lake Road, Roclty River, Ohio, and Edwin A. Corns, Rocky River, Ohio; said Corns assignor to said Wilson Fiied Feb. 13, 1957, Ser. No. 639,939 4 Ciairns. (Cl. 26340) This invention relates to methods of and apparatus for annealing coils of strip metal.

In a presently widely practiced procedure for annealing coils of strip metal, particularly mild cold rolled steel strip having a thickness of about .008" to about .0625" and a strip width of 24" to 96 in coils from about 40" to about 72 in outside diameter, either single coils or a plurality of stacked coils are placed on a furnace base with their axes vertical. When several coils are so stacked the individual coils are usually spaced apart by coil spacers or convectors designed to permit the heated gas to flow across the horizontal ends of the coils. The charge of coils on the base is enclosed by a sheet metal inner cover which has a suitable gas seal with the furnace base and the air within the inner cover is purged by forcing a suitable inert or de-oxidizing gas into the space within the inner cover. A bell-type heating furnace is then placed over the inner cover.

The base structure of a furnace of this type includes a fan or blower which is adapted to circulate the atmosphere within the inner cover around and between the coils in order to increase the convection transfer of heat to the coils. Heat is applied by any suitable means, such as combustion tubes carried by the furnace bell, and the coils are heated partly by radiant heat to the outside cylindrical surface of the coils and partly by convection heat transfer to the ends of the coils. The heat thus applied is eventually conducted by the metal of the coil until the temperature of the entire coil becomes sufiiciently high and sufiiciently uniform to achieve the desired results. Cooling of the coils is accomplished by a reverse procedure.

Such heating and cooling produces satisfactorily annealed coils of strip but, because of the dimculty of transferring heat to and from the tightly wound coils to achieve the required heating and cooling of the entire mass thereof, a complete annealing cycle, including heating, soaking and cooling, commonly takes a relatively long time. It is, therefore, an object of the present invention to provide a method of and apparatus for annealing coils of strip metal whereby the time required to bring the metal of all parts of the coil up to annealing temperature, maintain this temperature for the necessary soaking period, and then cool it down to the proper temperature, is very materially reduced from any previously proposed procedure for annealing coils of strip metal with which we are familiar.

Other objects of our invention include the provision of an improved method of and apparatus for annealing strip metal wherein the output of annealed product is large relative to the capital investment in the apparatus required; the provision of a method of and apparatus for annealing strip metal in coils whereby the cost per unit of output is substantially reduced as compared to prior coil annealing practices; the provision of a method of and apparatus for applying heat by convection to strip metal in coil form in an extremely rapid and uniform manner throughout the entire coil; the provision of a method of annealing strip metal having high thermal efficiency; and the provision of apparatus for annealing strip metal in coil form which is economical to build and install relative to its output capacity as compared to prior annealing apparatus, and which requires a minimum of upkeep and maintenance.

The above and other objects of our invention will appear from the following description of certain embodiments thereof, reference being had to the accompanying drawings, in which:

FIGURE 1 is a plan view of a re-coiling apparatus, adapted for use in carrying out our improved method, in which a tightly wound coil is shown being wound into an opened coil.

FIGURE 2 is a plan view similar to FIGURE 1 but illustrating the apparatus being employed to re-coil an opened coil back into a tightly wound coil upon completion of the annealing operation.

FIGURE 3 is a side elevation of the apparatus shown in FIGURE 1 being employed for the same purpose as FIGURE 1.

FIGURE 4 is an enlarged view taken substantially on line 4 4 of FIGURE 3 and illustrating the strip back tension brake apparatus.

FIGURE 5 is a vertical cross-sectional view through an improved annealing furnace and atmosphere circulating apparatus for carrying out the heating and cooling steps of our improved process.

FIGURE 6 is a horizontal cross-scetional view taken substantially on line 6-6 of FIGURE 5 and illustrating the coil loading rack or grid.

FIGURE 7 is a horizontal cross-sectional view taken substantially on line 77 of FIGURE 5 and illustrating the plenum chamber of the furnace base structure.

FIGURE 8 is a fragmentary cross-sectional view taken substantially on line S8 of FIGURE 7.

FIGURE 9 is a horizontal cross-sectional view taken substantially on line 99 of FIGURE 5 and illustrating the furnace charge support and diffuser.

Our improved method of annealing strip metal may be carried out in a bell-type furnace generally like that described above. It contemplates first re-coiling the usual tightly wound coil, which comes from the rolling mill with its laps or convolutions in close engagement with each other, into an opened coil in which the successive laps of the opened coil are spaced apart and the passages or openings therebetween are unimpeded. To maintain substantially uniform spacing and unimpeded passages between the laps this opened coil is supported at all times with its axis vertical and with the bottom end of the coil supported in a substantially horizontal plane on a grid or other suitable support. The opened coil is next heated to the desired annealing temperature in a suitable furnace. such as will be described later, by positively forcing heated gas to flow vertically, either upwardly or down- Wardly, through the unimpeded passages between the laps of the opened coil. Cooling is expedited by continuing to force the gas through said passages after the heat source is shut off.

As substantially the entire surface of both sides of the strip which makes up the opened coil is in direct contact with the gas flowing through the passages between the laps, convection heating and cooling may be effected at a very high rate and the entire mass of the metal of the coil may be brought up to the desired annealing temperature in a very short time as compared to that required to bring tightly wound coils up to the same temperature. Furthermore, this rapid heating may be obtained with a heating gas temperature only slightly higher than the maximum metal temperature to be obtained. 7 I

After the coil reaches annealing temperature it is maintained thereat by continuing the flow of heated gas vertically through the passages between laps for such time as is necessary to effect the desired annealing whereupon the application of heat is stopped but the forced flow of the gas vertically through the spaces is continued to effect rapid cooling of the coil by heat transfer from the strip to the gas and thence to the outside through the wall of the enclosure in which the annealing operation takes place.

After completion of the heating and cooling cycle the opened coil is re-coiled back into a tightly wound coil while still maintaining the strip and the axis of the opened coil substantially vertical to prevent undesirable shifting of the laps to one side or the other of the coil axis with possible resulting contact between the surfaces thereof and damage thereto.

By carrying out our above described method a coil of strip 36" wide and .035 thick having an inside diameter of 24" and an outside diameter of 52" can be put through the entire annealing cycle, i.e., heating, soaking and cooling, in approximately 8 /2 hours as compared with approximately 40 hours required to effect the same anneal ing cycle by' the prior procedure described above in which a tightly wound coil is heated solely by the application of heat against its outer cylindrical surface and across its top and bottom ends.

Although our invention is not strictly limited to any particular lap spacing relative to strip thickness we have found that advantageous results are obtained, so far as heating and cooling time, fuel costs, overall efficiency, etc. are concerned, when the radial dimension of the passages between the laps of the opened coil is from about one-half to about three times the thickness of the strip of the coil. The most effective and economical lap spacing varies to a degree with the thickness and width of the strip of the coil being treated. Thus, for a given strip width, with relatively thin strip (for example from .008 to .02" in thickness) the width of the space or passage between the laps may be less, relative to the strip thickness, than with coils of relatively thick strip (such as .006 to .015). The width of the strip of the coil also has an influence on the most desirable space between laps of the opened coil and, generally speaking, the wider the strip the greater should be the spacing between laps.

As previously noted, the original tightly wound coil, the opened coil, and the final tightly wound and annealed coil of strip are all maintained at all times during our process with their axes substantially vertical and their bottom ends (made up of the bottom edge of the coil convolutions) in a substantially horizontal plane. This maintenance of the vertical axis positioning enables the opened coil to be formed with uniform and unimpeded spacing between the laps and to be then transported to the annealing furnace without material shifting of the position of the laps, even though there are no spacers or other separating means therebetween. The vertical axis position thus maintains the desired unimpeded spacing between laps which permits flow of the heating gas over all parts of the surface of the strip, even to the interior of the body of the coil, with consequent uniform and very rapid heating thereof. With the axis of the opened coil vertical the strip is supported on its lower edge and it is the frictional engagement of this lower edge with the supporting grid or plate which holds the coil laps in proper spaced relation during annealing without any separate physical spacing means whatever. Re-coiling into tightly wound form without such contact or rubbing of the adjacent laps as might cause surface marring is also facilitated by maintaining the axes of the coils vertical.

By providing free, clear and unimpeded passages between the laps of the opened coils we achieve extremely uniform heating and cooling and consequent uniform annealing of the entire strip. With our procedure no spacing strips, surface projections, etc. are necessay to maintain the desired lap spacing during the annealing operation. Thus there is no surface marring as would be caused by such spacing elements, no interference with free and uniform flow of the heating gas over the face of the strip, and no edge trimming required after annealing.

Referring now to the drawings, an apparatus for carrying out our improved annealing process will be described. In this apparatus, and in the procedure carried out therewith, the spacing of the laps of the opened coil is accomplished by winding into the open coil, adjacent the top end thereof, a spacer strand or cord of suitable size and material. After forming the opened coil, and before it is transferred to the annealing furnace, this spacer cord is withdrawn from the coil, thus providing completely open and unimpeded passages between the laps. Although in the illustrated apparatus a spacer cord or strand is employed in forming the opened coil, our improved method contemplates the forming of the opened coil by other procedures wherein no spacer is employed. It will also be understood that although we have referred to the spacing between the laps of the open coil as uniform, in practice there may be slight variations in spacing, and even contact between a few laps of a given coil, without substantial effect on the annealing operation and such variations are intended to be included where the spacing is defined herein as being substantially uniform.

The re-coiling steps of our process, in which a tightly wound unannealed coil from the rolling mill is converted into an opened coil and the annealed opened coil is recoiled back into a tightly wound coil, all while maintaining the axis of the coils vertical, may be carried out by the apparatus which is shown in FIGURES 1-4 inclusive. This apparatus includes a freely rotatable payoff turntable 1 in the form of a flat disk carried by a vertical shaft or axle 2 which in turn has a suitable bearing in the base member 3. The turntable 1 is a additionally supported adjacent its outer periphery by a series of circumferentially spaced idler rolls 4 which are mounted in suitable brackets 5 on the top of the base 3. These idler rolls 4 are freely rotatable and thus it will be seen that the turntable 1 may rotate in a horizontal plane with a minimum of frictional resistance while supporting a load thereon.

A coil loading rack R, which will be described in more detail later, is placed on top of the turntable l and the tightly wound unannealed coil C is supported thereon with its axis vertical. Secured to and carried by the turntable 1 is a guide mandrel member 6 which extends upwardly through a center opening in the coil loading rack R into the interior of the coil C and serves to center both the coil loading rack R and the coil C on the turntable 1.

A power driven re-coiling turntable 7 is supported on a base structure 8 which is spaced a suitable distance from the freely rotating pay-off turntable l. Turntable 7 is carried by a central vertical shaft 9 and is supported at its outer periphery by a series of idler rollers 9' which are similar in function and arrangement to the idler rollers 4. The shaft 9 extends downwardly into and is supported in the gear box 10 and is positively driven through suitable gearing in the box 10, the pulley 11, belt 12, speed reducing pulleys l3 and 14, belt 15 and reversible electric motor 16. By suitable electrical connections (not shown as they may be of any well-known type) the motor 16 may be driven in either direction thereby causing the turntable 7 to be rotated in the corresponding direction through the driving connections described above.

Carried by the driven turntable '7 and centered relative to the vertical axis of rotation thereof is an upwardly extending cylindrical collapsible spindle or mandrel l7 having any suitable type of collapsing and strip end gripping means indicated at 18. During re-coiling operations the end of the strip to be re-coiled is secured to the mandrel 17 by the gripping means 18 and, upon rotation of the driven turntable 7, with accompanying rotation of the mandrel 17, the strip will be wound therearound.

Disposed between the freely rotatable pay-off turntable 1 and the power driven re-coiling turntable 7 is a back tension brake apparatus, generally indicated at B, which is adapted to impose the desired amount of back tension on the strip as it is being re-coiled. This brake apparatus is illustrated in FIGURES l, 3 and 4 as it is set up for applying back tension to the strip during the initial recoil-ing of the tightly wound unannealed coil into an opened coil. In FIGURE 2 it is illustrated as set up for applying back tension during re-coiling of the opened annealed coil back into a tightly wound coil.

As best seen in FIGURE 4, the back tension apparatus includes a vertical, freely rotatable strip guiding and back-up roll 19 supported in suitable bearings 20 carried by the brake apparatus frame 21. Also pivotally supported on the frame "21 are three bell crank levers 22. As seen in FIGURES l and 3 these bell crank levers are supponted on pivot pins 23 carried by one of the vertical side members of the frame structure 21. Each of the three bell crank levers 422 has pivotally secured thereto a bracket 24 and each bracket 24 carries in turn a brake shoe member 25. As illustrated the brake shoes 25 consist of Wooden blocks, preferably contoured on the side adjacent the roll 19 to correspond to the curvature of the roll.

At the outer end of each bell crank lever 22 is a weight 26 and it Will be seen that, due to the pivotal support of the bell crank levers 22 on the pins 23, the weights 26 will urge the brake shoes 25 toward the roll 19. When the strip S (FIGURE 1) leaves the tightly wound unannealed coil C it passes over the roll 19 and the brake shoes 25 impose a frictional load or \drag on the strip which creates a back tension that is effective to cause the strip to be re-coiled around the mandrel 17 on the re-coiling turntable 7 with the desired degree of tightness. This back tension may be varied by changing the weights 26, increasing the weights causing increased back tension and decreasing the weights causing reduced back tension.

As will appear more fully later, when an annealed opened coil C is to be re-coiled back into an annealed tightly wound coil C, as seen in FIGURE 2, the strip S is passed over the opposite side of roll 19 from that engaged by the strip during the initial coil opening operation shown in FIGURE 1. To enable back tension to be applied during the second re-coiling step of FIGURE 2, pivot pins 27, similar to pivot pins 23, are mounted on the opposite vertical side member of frame structure 21 of the back tension apparatus. Prior to the final recoiling operation illustrated in FIGURE 2 the bell crank levers 22, with their brake shoes 25 and the weights 26, are removed from the pins 23 and placed on the pins 27. This disposition of the bell cranks 22, etc. is seen in FIG- URE 2 and thus back tension may be created on strip S during the final re-coiling step.

It will be understood that, if desired, two complete sets of brake shoe supporting bell crank members might be mounted on the frame 21, thus eliminating the necessity for transferring same from one side of roll 19 to the other, or that any other suitable means for creating back tension on the strip S might be employed.

As previously explained, in order to form an opened coil from a tightly wound unannealed coil we propose to re-coil the tighlty wound coil and during the re-coiling operation to interwind a spacer strand or cond between the laps of the rewound coil. This operation is shown being carried out in FIGURES 1 and 4 of the drawings in which the strip S from the tightly Wound coil C, which is supported on a coil loading rack R which in turn is supported on the freely rotatable turntable 1, has been passed through the back tension brake apparatus B and the end of the strip secured to the mandrel 17 by the gripper 18. A second coil loading rack R is placed on the driven turntable 7 so that the opened coil will be formed thereon and may be properly handled during further processing. When the motor 16 is actuated to drive the turntable 7 and mandrel 17 in clockwise direction as seen in FIGURE 1 the strip S will be pulled from the tightly wound coil C and wound around the mandrel 17.

To space the laps of the re-wound coil C apart and thus form an opened coil, we provide a spool 28 carrying a quantity of spacer cord 29. This cord may be round or fiat in cross section and its thickness radially of the coil C is, as noted heretofore, preferably between about one-half and three times the thickness of the strip being handled. The cord or strand may be metallic or nonmetallic and of twisted, braided, or monofilament form. Monofilament nylon of proper diameter has been found to be very satisfactory as a spacer strand material, having long life, great strength, and being easily pulled out after the coil opening operation is completed.

The spool 28 is securely mounted on the horizontal shaft 3% of the spool support and cord re-winding apparatus which is generally indicated at A. During the forming of the opened coil the shaft 30 is adapted to rotate freely and thus permit the cord 29 to be unwound from the spool 28. A level-wind guide for the cord 2 is seen at 31 and this guide is adapted to be oscillated back and forth parallel to the axis of shaft 3&9 and spool 23 by a suitable double helirr thread member 32 which in turn is driven in synchronism with the shaft 30 by interconnecting drive means which include a belt 33 and gear box 34. As will be later fully described, when it is desired to remove the spacer cord 29 from the opened coil C the spool 28 is driven in the opposite direction by a motor 35. Suitable clutch means, not shown, are preferably provided between the motor 35 and the shaft 3t) whereby, during the coil opening operation While the spacer cord is being interwound between the laps of the coil, the motor 35 may be disconnected from the shaft 30, thus permitting it, and the spool 28, to rotate freely. When it is desired to withdraw the cord 29 and Wind it back on the spool 23 the clutch is engaged and the motor actuated to drive the shaft St in wind back direction.

As seen in FIGURES 1 and 3 the spacer cord 29 is shown in :full lines as it is being wound into the opened coil C, and its path during the cord withdrawing operation is indicated by dot and dash lines. As the start of the coil opening end of the cord or strand 29 is passed upwardly through a guide 36 adjus-tably supported on a vertical stanchion 37 at the proper height for the width of strip being handled and then is carried transversely in a substantially horizontal direction and inserted between the initial inside lap of the rewound coil C. As seen in FIGURE 3 the cord 29 is guided into the laps of the rewound coil C a short distance down from the upper end of this coil (for example 1 to 2"). As the motor 16 rotates the turntable 7, coil loading rack R and mandrel 17 in clockwise direction the strip will be wound upon the mandrel 1'7 and spacer cord 29 will be drawn from the spool 28 and wound in between the successive laps of the coil. Proper back tension is applied to the strip S by the back tension brake apparatus B with the result that the laps of the opened coil C will be substan tially uniformly spaced apart by a radial distance equal to the radial dimension of the spacer strand 29'.

When the strip S is completely re-coiled from the original tightly wound coil C into an opened coil C supported on a coil loading rack R on the turntable 7, and with the spacer cord 29 between each lap thereof, the drive motor 16 is stopped. In order to remove the spacer cord 29 from between the laps of the opened coil C and establish completely free and unimpeded passages between said laps of the coil, a portion of the cor-d 29 between the guide 36 and the coil C is lifted and placed in an upper guide 33 which is carried on a horizontal arm 39 supported on a vertical stanchion 40. The arm 39 may be swung about the axis of stanchion 40 from the cord removing position seen in FIGURES l and 3 into withdrawn position seen in FIGURE 2 to permit loading and unloading of the turntable 7.

When the arm 39 is in cord removing position the guide 38 is preferably disposed substantially directly above the center of the coil C. The motor 35 now being operated to wind the strand 29 back onto the spool 28, the strand will be pulled upwardly out of the gap or space between the laps of the coil C without excessive resistance or drag of the strand over the edges of the strip. This cord removing operation can be performed with great rapidity and without twisting the strand, and when the rewinding operation is complete the spacing strand 29 is back on the spool 28 ready for the next coil opening operation.

When the above described re-coiling operation is completed and the spacer strand has been removed the opened coil C is supported on the coil loading rack R which in turn rests on the turntable 7. The individual laps of the coil are substantially uniformly spaced apart by a distance substantially equal to the thickness of the spacer strand which was employed. Due to the frictional engagement of the lower edge of the strip on the upper surfaces of the rack R (which, as will he later described, is a grid-like structure) the individual laps of the coil will remain in their spaced apart positions and the spacing will be substantially uniform from top to bottom of the coil. The opened coil C is then transported to the annealing furnace on the rack R, by a suitable crane or other handling apparatus, while maintaining the top face of the rack R substantially horizontal and the axis of the coil substantially vertical. A furnace adapted to carry out our process is seen in FIGURES 9 and includes a base structure generally indicated at D, a plenum chamber generally indicated at E, an inner cover generally indicated at F, and a furnace bell generally indicated at G.

The furnace base D is supported on a suitable foundation 41 and is adapted to carry the charge and the weight of the inner cover and furnace bell. A centrifugal type fan or blower 42 has a vertical shaft 43 extending through the furnace base B and supported in a suitable bearing 44-. The lower end of shaft 43 projects below the bearing and carries a pulley for the drive belt 45 which in turn is driven by a suitable motor (not shown).

Surrounding the fan 42 is a charge support and diffuser structure which, as seen in FIGURES 5 and 9, includes a circular bottom plate 46, an outer cylindrical vertical wall 47 and an inwardly inclined, generally conical, gas diverting face is. The bottom plate 46 has center hole 4? to permit the fan shaft 43 to pass therethrough and a plurality of streamlined diffusing vanes 50 are circumferentially spaced around the bottom plate 46, being secured thereto and extending vertically upwardly therefrom. The inner ends of the vanes 5t) lie on a circle slightly larger in diameter than the outside diameter of the fan 4-2 and the outer ends of the vanes are contoured to fit the inclined face i3. As is seen in FIG- URE 5, the vanes 5t} have a greater vertical height than the wall portions 47 and 4S and short intermediate vanes 51 may be disposed near the outer periphery of the diffuser to assist in controlling the flow of atmosphere from the fan 42.

Supported on top of the vanes 5G is the plenum chamber E. This is seen in FEGURES 5, 7 and 8 and consists of a circular base plate 52 having a circular central opening 53 disposed above the fan 42 and of a diameter substantially equal to the fan inlet. A vertical cylindrical outer wall 54 is secured to the base plate 52 at its outer periphery and a plurality of radially inwardly extending vertical fins 55 are welded to the base plate 52 and outer wall 54. The inner ends of these fins 55 are inclined as indicated at 55 in FIGURE 5 so that their top edges are somewhat longer than their bottom edges. A conical flow guide member 56 is supported at its upper end by the upper inner corners of fins 55 with the apex pointing downwardly toward the center of fan 42. The baflle plate or disk 57 covers the open upper end of the conical flow guide 56. Between each adjacent pair of fins S5 is an inclined segmentally shaped plate 58 which is secured at its outer end to the outer wall 54 and at its inner end to the base plate 52 adjacent the central opening 53 therein. These segmental plates 58 are also preferably welded along their side edges to the adjacent fins and serve to reinforce and support the fins 55 as well as to define, with the conical member 56, the desired gas flow path to the upper inlet opening of the fan 42. As seen in FIGURES 7 and 8, each of the fins 55 is also preferably supported by angle brace bars 49 which extend from opposite sides of each fin to the base plate 52.

The inner cover F is adapted to enclose the furnace charge and to retain the desired furnace atmosphere. It also facilitates the heating of this atmosphere and its circulation into contact with the charge. As illustrated the inner cover F consists of an open bottomed generally cylindrical sheet metal structure having an outer wall 60, a closed top 61, and an inner wall 62 concentric with but inwardly spaced from outer wall 69. The lower end 6b of outer wall d8 rests upon the furnace base D. An outwardly extending skirt member 63 is carried by the wall 64 and has downwardly extending cylindrical flanges and 65 at its outer edge. These flanges fit in corresponding troughs 66 and 67 in the furnace base and the troughs are filled with liquid or sand to provide an effective gas seal to prevent the undesired entry of outside atmosphere into the space within the inner cover F.

Tne cylindrical inner wall member 62 of the inner cover F is supported by the outer wall 64) for limited vertical movement relative thereto. As seen in FIGURE 5 the inner wall 62 terminates short of the top and bottom of the wall 60 and rests at its bottom edge on top of the outer wall portion 54 of the plenum chamber E. Suitable lifting rings or the like (not shown) are provided on the inner cover F to facilitate its removal when it is desired to load or unload the furnace base.

The furnace bell G may be of any suitable and conventional form well-known in this art. As illustrated it consissts of an insulated cylindrical structure closed at the top and open at the bottom. Heat is supplied to the furnace by a plurality of combustion tubes 68 supported in the wall of the bell and disposed around its inner circumference. These tubes are supplied with a suitable mixture of fuel and air and furnish the heat necessary for the annealing operation. When in operating position the bell G rests upon the furnace base D and it may be removed for loading or unloading the furnace independently of the inner cover F by the lifting eye 69.

As previously noted, during the coil opening operation both the pay-off turntable 1 and the re-coiling turntable 7 support coil loading racks R. One of these racks is seen in plan view in FIGURE 6 and it includes an outer ring or rim 7t}, an inner ring 71, and radial spoke members 72 extending from ring '71 to ring 79. Circumferentially extending struts 73 serve to brace and reinforce the grid-like structure and short intermediate spokes 74 extend from the struts 73 to the outer rim 70. The spokes 72 and 74 are preferably of I-beam section having a web portion 72', a top flange portion 72 and a bottom flange portion 72" as indicated in FIGURE 6 in which parts of two of the spokes are broken away.

As the vertical height of the various spokes and struts is the same as that of the inner and outer rings 70 and 71 (see FIGURE 5) each of the coil loading racks R provides a grid-like support for a coil and may be used either side up. As the top surfaces of the spokes 72 and '74 and struts 73 all lie in the same plane, when an opened coil is supported on one of the racks R the lower edges of the strip rest upon the upper surfaces of the spokes and struts with sutficient frictional engagement to prevent shifting of the laps relative to each other while permitting free flow of gas through the passages between the laps.

In use of the furnace apparatus described above to carry out our improved process the furnace bell G and the inner cover F are removed from the base D when a coil is to be placed thereon for annealing. An opened coil C, supported on a rack R, is lifted from the re-coiling turntable 7 and is transported to the furnace base, maintaining the coil axis at all times substantially vertical, and the rack R with the coil C thereon is placed on top of the plenum chamber E with the center ring 71 of the rack R fitting over and being centered by the bafile plate 57 of the plenum chamber. The fins 55 of the plenum chamber engage the underside of rack R and afford the necessary support without undesirable interference with the flow of the furnace atmosphere during annealing.

Next the inner cover F is placed in position over the furnace charge with its inner wall portion 62 resting on and in substantial sealing engagement with the outer wall 54 of the plenum chamber B. After the inner cover is properly positioned the furnace bell G is placed over the entire unit. In order to purge the air within the inner cover F a suitable gas is forced into the space within the inner cover through the inlet pipe 75 which has suitable connections (not shown) through the base D to the interior of the inner cover F. A gas outlet pipe 76 is provided to permit the air purged at the start of the operation to be discharged and also to permit a controlled outfiow of the annealing atmosphere gas during the annealing operation.

When the air is purged from the inner cover F heat is applied by the combustion tube 63 and the blower fan 42 circulates the atmosphere within the inner cover as indicated by the arrows in FIGURE 5. The gas moves outwardly from the periphery of the blower 42 between the vanes of the diffuser and when it reaches the outer portion thereof it is directed upwardly by the inclined diverting plate 43 and passes out into the space between the outer wall 54 of plenum chamber E and outer wall 60 of the inner cover. It will be understood that the base plate 52 of the plenum chamber forms a cover plate for the diffuser section and the only outlet for gas from the diffuser is around the outer circumference above the top edge of the outer wall 47. The gas now moves upwardly in the annular chamber defined by the outer wall 54 of the plenum chamber E and the outer wall 60 of the inner cover.

As previously noted, the inner wall 62 of the inner cover F rests upon outer wall 54 of the plenum chamber E and in effect forms an extension thereof and thus the annular passage through which the gas moves upwardly extends to the top of inner wall 62 adjacent the top of the inner cover F. As the combustion tubes 68 are closely adjacent the outer wall 60 of the inner cover the upwardly moving gas is rapidly and effectively heated during this upward travel. When the hot gas is discharged into the space between the top 61 of the inner cover F and the top of the coil C it cannot move downwardly through the center opening 77 in the coil C because the bottom end of this opening is effectively closed by the baffle plate 57. Accordingly the gas must move vertically downwardly through the passages P between the laps L of the opened coil C. This downward movement is possible because of the open grid-like support provided by the rack R and is facilitated by the substantially open plenum chamber E which is connected directly to the inlet of fan 42 and causes the gas to be drawn down through the unimpeded passages P between the laps L of coil C.

Because of the substantially complete exposure of both sides of the entire length of the strip making up the coil C to the heated moving gas within the inner cover F extremely rapid heating of all parts of the coil up to the desired annealing temperature may be obtained.

In the annealing of tightly wound coils as practiced in the past, the total maximum surface area which may be exposed to heat is the area of the two end faces of the coil plus the area of the outer and inner cylindrical surfaces of the coil. As a practical matter only the end faces of the coil are of substantial effect because travel IQ of heat radially of the coil from the inner and outer surfaces is extremely slow, the contact between adjacent laps not being such that good transfer is effected therebetween. With our opened coil procedure, however, the area exposed to direct convection heating is the entire area of both sides of the full length of strip making up the coil plus the same surfaces as are available when a tight wound coil is annealed. This tremendously increased exposed area, and the forced, high velocity flow of heated gas thereover, make possible heating of a given length of strip by our method in a small fraction of the time previously required.

By moving the gas through the passages between the laps under positive pressure and at relatively high velocity the interior and bottom portions of the coi may be brought up to temperature much more quickly than is possible by application of heat only to the outer face and ends of a tightly wound coil where no fiow between laps is possible.

When the desired annealing temperature is reached, it is maintained by proper control of the heat applied throughout combustion tubes 8 for the desired soaking period. The bell G is then removed and circulation of the gas within the inner cover is maintained by the fan 42 during the cooling portion of the cycle. The time required for cooling is also greatly reduced from that of previous practices because of the positive high velocity flow of gas over substantially the entire surface of the strip with resulting extremely rapid transfer of heat from the coil to the outside atmosphere through the walls of the inner cover F.

After the desired cooling has been effected the inner cover F is removed and the rack R, together with the opened annealed coil C, is lifted from the furnace and carried over and placed on the pay-off turntable 1. While so moving this opened annealed coil its axis is maintained in a vertical position and thus the spaced laps of the coil do not shift radially. The end of this opened coil is then passed over the guide and back-up roll 19 of the back tension apparatus B on the opposite side thereof (see FIGURE 2) from that of the original coil opening operation, the bell crank arms 22 and brake shoes 25 having been shifted into the positions seen in FIGURE 2.

After the end of the strip is gripped in the strip gripper 18 of the collapsible mandrel 17 of the re-coiling turntable 7 the motor 16 is operated to drive the turntable and mandrel in counter-clockwise direction and the strip will then be tightly wound into a finished annealed tight coil C. When this final tight re-coiling operation is completed the mandrel 13 is collapsed and the finished coil lifted from the rack R of turntable 7 on which it was re wound. Proper back tension is, of course, applied to the strip during this operation by means of the brake shoes 25 to effect proper tight winding.

After the bell crank arms 22 and brake shoes 25 are moved back into the positions seen in FIGURE 1, the recoiling apparatus is ready for another coil opening operation. During the re-coiling of the annealed opened coil into a tight annealed coil, the horizontal arm 39 for carrying the overhead spacer strand guide 38 is swung out of the way as seen in FIGURE 2 and the spacer strand 29 remains on its spool 28.

By supporting the coils on the grid-like racks R during the re-coiling operations and the annealing procedure, and by maintaining these racks substantially horizontal at all times so that the coil axes remain in a vertical position, the necessity for maintaining a spacer mem ber between the laps of the opened coil during annealing is eliminated. This makes possible the free unimpeded flow of furnace atmosphere at high velocity between the laps over the entire strip surface. Furthermore, by removing the spacer strand prior to annealing, marr-ing or discoloration of the strip, which would occur if the strand were left in during annealing, is completely eliminated and thus no edge trimming after annealing is required.

Although we have described in considerable detail our improved process and one form of an apparatus for conducting same, it will be understood that variations and modifications may be made in the procedure and in the apparatus used for carrying it out without departing from the spirit of our invention. We do not, therefore, wish to be limited to the specific steps and structures herein described but claim as our invention all embodiments thereof as coming within the scope of the appended claims.

We claim:

1. In a furnace for annealing opened coils of strip etal, an open grid structure supported adjacent the bottom of said furnace and having a coil supporting surface adapted to support an opened coil with its axis substantially vertical, wall means for confining a body of atmosphere around said opened coil on said grid structure, blower means for circulating said body of atmosphere within said walls, bafile plate means for closing the center opening in said opened coil whereby the how of atmosphere therethrough is bi cked, and battle wall means disposed in spaced relation below said coil supporting surface of said open grid structure and substantially coextensive in a horizontal direction with said grid structure, said baffle wall means being disposed, with said baiiie plate means, to direct substantially the entire volume of said confined body of atmosphere vertically through the passages between the spaced apart laps of said opened coil.

2. The method of annealing strip metal which includes the steps of re-coiling an unannealed tightly wound coil of said strip metal into an opened coil by interwinding a spacer strand between the successive laps of the strip during said re-coiling whereby said laps are positively and substantially uniformly spaced apart by a distance substantially equal to the radial thickness of the spacer strand and not less than about one-half the thickness of the strip and not more than about three times the thickness of the strip, removing said spacer strand while holding said coil stationary whereby an opened coil is formed having unimpeded passages between the laps thereof, maintaining said laps in spaced apart relation solely by frictional engagement of the lower edge of the strip with the structure on which the opened coil is supported, and subjecting said opened coil to annealing temperature by forcefully and repeatedly circulating substantially the entire volume of a confined body of heated gas vertically through the major portion of said unimpeded passages for a period sutiicient to effect heating of said strip to annealing temperature largely by convection heat transfer from said gas, all while maintaining the strip and the axes of the coils in which it is wound substantially vertically disposed without inversion.

12 3. Apparatus for preparing coils of strip metal for annealing including a rotatable coil supporting pay-off turntable, a power driven coil supporting re-coiling turntable, said turntables being spaced apart from each other and rotatable in substantially the same horizontal plane, means for supporting a spool of spacer strand for rotation in one direction to pay-01f said strand from said spool, means for guiding said strand during pay-off in a horizontal direction into the laps of a coil being formed on said re-coiling turntable and adjacent the top of said coil, driving means for rotating said spool in a direction to pull said strand from between the laps of said coil and rewind same back on said spool, and means for guiding said strand in a generally vertical direction to a point substantially on the vertical axis of the coil while withdrav inn same from between the laps of said coil.

4. In apparatus for handling and annealing strip metal, a pay-oh turntable supported for rotation in a substantially horizontal plane, a re-coiling turntable spaced from said pay-oft turntable and rotatable in a substantially horizontal plane, power actuated means for rotating said recoiling turntable, a collapsible mandrel coaxially supported on and secured to said re-coiling turntable, means for removably supporting coils of strip metal on said turntables, back tension creating means disposed between said turntables and adapted to exert back tension on strip being re-coiled on said mandrel, a spool of spacer strand ro tatably supported adjacent said re-coiling turntable, means for guiding said spacer strand in a horizontal direction between the laps and adjacent the top of a coil of strip being re-coiled on said re-coiling turntable, means for rotating said spool in a direction to withdraw said spacer strand from between the laps of said coil, and means for guiding said strand in a generally vertical direction from between the laps of a coil on said re-coiling turntable to a point substantially on the vertical axis of said coil, all whereby an opened coil having unimpeded passages between the laps thereof may be formed on said re-coiling turntable.

References Cited in the file of this patent UNITED STATES PATENTS 1,938,306 Webb Dec. 5, 1933 2,169,314 Wilson Aug. 15, 1939 2,224,997 Weisse Dec. 17, 1940 2,321,146 Jones June 8, 1943 2,409,384 Peterson Oct. 15, 1946 2,479,809 Bohlin Aug. 23, 1949 2,613,070 Verwohlt Oct. 7, 1952 2,658,694 Koch Nov. 10, 1953 2,769,630 Keller Nov. 6, 1956 

1. IN A FURNACE FOR ANNEALING OPENED COILS OF STRIP METAL, AN OPEN GRID STRUCTURE SUPPORTED ADJACENT THE BOTTOM OF SAID FURNACE AND HAVING A COIL SUPPORTING SURFACE ADAPTED TO SUPPORT AN OPENED COIL WITH ITS AXIS SUBSTANTIALLY VERTICAL, WALL MEANS FOR CONFINING A BODY OF ATMOSPHERE AROUND SAID OPENED COIL ON SAID GRID STRUCTURE, BLOWER MEANS FOR CIRCULATING SAID BODY OF ATMOSPHERE WITHIN SAID WALLS, BAFFLE PLATE MEANS FOR CLOSING THE CENTER OPENING IN SAID OPENED COIL WHEREBY THE FLOW OF ATMOSPHERE THERETHROUGH IS BLOCKED, AND BAFFLE WALL MEANS DISPOSED IN SPACED RELATION BELOW SAID COIL SUPPORTING SURFACE OF SAID OPEN GRID STRUCTURE AND SUBSTANTIALLY CO- 